[CP2K:1053] Velcoities printed are different

[Teodoro Laino]

Rad,

>    &CONSTRAINT
>      CONSTRAINT_INIT  T
>      &FIXED_ATOMS
>        RANGE               1         2
>      &END FIXED_ATOMS
>    &END CONSTRAINT

> If you compare the initial set of velocities with the ones in the
> input, you can see that they are different. Is it a bug in cp2k or the
> velocities are converted to a different unit or somehow the velocity
> of the center of mass is subtracted?
Normally velocities (when read through the input file) are just accepted
as they are (no postprocessing, i.e. rescaling or vcom removal).

But in your case you're explicitely asking for

CONSTRAINT_INIT

what this keyword does is:
(1) apply constraints at the 0 step of the MD (so that you don't see  
any jump between the
step nr.0 and the nr. 1 in the energy)
(2) after application of constraints rescale consistently the initial  
energy of the system..

Now in your case you don't have any constraint that requires  
specifically the application
of initial constraints, because fixed atoms have just to stay fixed  
(the story is different if you
want to keep bonds constrained or anything else).
But since you asked for :

CONSTRAINT_INIT

this means that once the velocities of the fixed atoms are nullified  
the velocities of the all particles
are scaled in such a way to get the requested temperature.
If you dont' want that, please remove the keyword:

CONSTRAINT_INIT

No bugs at the moment  ;-)..
Cheers
Teo

>
> Could you please look into this and let me know where the issue might
> be. I got into this issue on my large system and so I tried it on a
> small test system and verify the consistency of the behaviour.
>
> Please let me know if you need any additional information on the test.
>
> Thanks
> Rad
> >